Q. A 35-year-old female presents to her primary care physician with a complaint of fatigue, weight gain, and cold intolerance for the past 6 months. The patient also reports feeling depressed and has experienced excessive hair loss. On physical examination, her thyroid gland is diffusely enlarged, smooth, and firm to palpation. She also has a low-grade fever and her heart rate is slightly elevated. Her laboratory results reveal an elevated thyrotropin level and a low free thyroxine level. She also has high levels of anti-thyroglobulin and anti-thyroid peroxidase antibodies. The patient reports no history of radiation exposure or thyroid surgery. Which of the following is the most likely diagnosis?